In a single bevel GMAW (gas metal arc welding) with gap fluctuation, a deep learning model was constructed using the monitoring image during the welding to predict the welding quality. We utilized ...Python and the library Keras and created a CNN (Convolutional neural network) model using the top surface image including the molten pool as an input. The classification model was used to predict the burn-through, and the regression model was used to estimate the penetration depth. As a result, the excessive penetration and burn-through could be predicted in advance and more than 95 % of estimated results of penetration depth were less 1 mm error for stepped and tapered sample shapes.
The article describes the advantages of laser + MAG hybrid welding method. The results of research hybrid welding of 5 + 5 and 5 + 7 mm butt joints S960QL steel and strength and toughness tests of ...obtained joints were presented. Testing of 5 + 7 mm thick butt joints showed that it meets the requirements of the PN-EN ISO 15614-14 standard. in polish Spawanie hybrydowe laser + MAG elementów urządzeń dźwigowych wykonanych ze stali ulepszonej cieplnie S960QL W artykule opisano zalety metody spawania hybrydowego laser+MAG. Przedstawiono wyniki badań spawania hybrydowego złączy doczołowych 5 + 5 i 5 + 7 mm ze stali S960QL oraz wyniki badań wytrzymałości, udarności i twardości uzyskanych złączy. Badanie złącza doczołowego blach o grubości 5 + 7 mm wykazało, że spełnia ono wymagania PN-EN ISO 15614-14.
Residual stresses are an important factor in the performance and stability of welded structures. This study investigates the characteristics and significance of residual stresses in MAG-welded ...ultrahigh-strength steel rectangular hollow sections. The research incorporates comprehensive X-ray diffraction residual stress measurements, electron backscatter diffraction analysis, statistical analyses, and finite element method simulations to provide valuable insights into the behaviour of welding residual stresses. The results reveal clear microstructural variations between the cold-formed corner and the flat side of the rectangular hollow section caused by welding heat input, emphasizing the need to consider these variations in residual stress assessments. Furthermore, the study examines the dependence of residual stresses on the steel grade, with higher strength steel exhibiting compressive stresses and lower strength materials experiencing tensile stresses in corner areas. Statistical analysis indicates that welding sequence and direction have negligible effects when applying the employed welding sequence. In any case, higher heat input leads to significantly larger residual stresses. Finally, the study presents a novel analytical model based on validated finite element simulations to predict the maximum variation of residual stresses depending on welding heat input. The findings provide valuable insights into the significance of welding residual stresses and their predictability. The comprehensive measurements, simulations and proposed models contributes to a better understanding of residual stress phenomena, facilitating the development of reliable design guidelines for welded structures in various engineering applications.
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•S700 and S960 UHSS hollow sections were welded and XRD-measured.•Residual stresses in cold-formed corner depends on steel grade: more compressive in S960 steel.•S700 steel contains higher welding residual stresses with relative to yield strength.•Welding FEM-simulation with initial residual stress state was validated by XRD-results.•Novel analytical models are proposed for predicting residual stresses in UHSS hollow sections.
Ultra-high power laser-MAG hybrid welding technology provides an effective method for joining thick plates with high-quality and efficiency. Heat source configuration of laser and arc was verified to ...play a vital role in conventional hybrid welding process. In this paper, ultra-high power laser-MAG hybrid welding was utilized to weld 20 mm thick Q235 steel for clarifying the effect of heat source configuration on welding process and joint formation. By high-speed photography, welding process was systematically recorded including hybrid plasma morphology, droplet orientation-transfer and molten pool flow. Subsequently, the joint formation was further analyzed via dynamic behaviors of liquid column and keyhole. Results exhibited that a stable arc characteristic and smooth molten pool flow was formed under HM (ultra-high power laser and MAG-leading) mode. Besides, the enlarged and stabilized keyhole would inhibit the height of liquid column and formation of spatters. Finally, a sound weld joint without “ant-colony-like defect” joint formation and 15.82 mm penetration was produced in HM mode. This work provides an effective method and reference for realizing thick plate single pass weldments in the practical industry.
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In this paper, the diameter of 1.2mm and 1.6mm welding wires were used to carry out high-frequency pulse MAG butt welding process test on S355J2W+N weathering steel. The analysis of the ...microstructure characteristics of the welded joints under the two working conditions shows that there is little difference and both are ideal. There were more acculate ferrite (AF), less pearlite (P) and bainite (BG), and no larger Weisserite structure and less ferrite side-plate (FSP) structure. The weld is well formed, weld defects such as gas pores and cracks are not found. The impact test showed that the impact energy Akv (-40 °C) of the welded joint at -40 °C was higher than the specified minimum impact energy of 27 J. Compared with the 1.2mm welding wire, the impact energy of the 1.6mm welding wire is lower. Tensile test results show that the fracture occurs at the base metal position. and the fracture height is uneven, forming an angle of 45° with the tensile stress direction, which is a ductile fracture. When the bending angle of the butt joint samples reaches 180°, no cracks are both found on the tensile surface, and the plastic index of the welded joint samples is qualified and has good bending performance.
This study was conducted to examine the immersion effect of cooling media used after the MAG welding process on impact toughness behavior of A36 steel plate. The media used in the experiment include ...air, water, and ice while CO2 shielding gas and ER70S-6 filler metal were used in the MAG process. It is also important to note that the speed of the weld material cooling process has the ability to affect the hardness and toughness of the post-welding product. The experimental results showed that the use of cooling media affected the impact properties of the welding joint. The highest toughness value was recorded in the ice cooling media with 4,38 J/mm2.
PurposeAn experimental investigation for developing structure-property correlations of hot-rolled E410 steels with different carbon contents, i.e. 0.04wt.%C and 0.17wt.%C metal active gas (MAG) and ...cold metal transfer (CMT)-MAG weldments was undertaken.Design/methodology/approachMechanical properties and microstructure of MAG and CMT-MAG weldments of two E410 steels with varying content of carbon were compared using standardized mechanical testing procedures, and conventional microscopy.Findings0.04wt.%C steel had strained ferritic and cementite sub-structures in blocky shape and large dislocation density, while 0.17wt.%C steel consisted of pearlite and polygonal ductile ferrite. This effected yield strength (YS), and microhardness being larger in 0.04wt.%C steel, %elongation being larger in 0.17wt.%C steel. Weldments of both E410 steels obtained with CMT-MAG performed better than MAG in terms of YS, ultimate tensile strength (UTS), %elongation, and toughness. It was due to low heat input of CMT-MAG that resulted in refinement of weld metal, and subzones of heat affected zone (HAZ).Originality/valueA substantial improvement in YS (∼9%), %elongation (∼38%), and room temperature impact toughness (∼29%) of 0.04wt.%C E410 steel is achieved with CMT-MAG over MAG welding. Almost ∼10, ∼12.5, and ∼16% increment in YS, %elongation, and toughness of 0.17wt.%C E410 steel is observed with CMT-MAG. Relatively low heat input of CMT-MAG leads to development of fine Widmanstätten and acicular ferrite in weld metal and microstructural refinement in HAZ subzones with nearly similar characteristics of base metal.
New ultrahigh-strength steels have been developed to meet the need for better performance, load bearing capacity, safety and weight saving. However, the design guidelines are incomplete, especially ...regarding the design of welded ultrahigh-strength steel components in fluctuating operating conditions. This reduces usability and can cause serious safety risks when the welded structures are in use. The heat input and cooling rate have a significant effect on the microstructure and mechanical properties of the ultrahigh-strength steels. Therefore, a model to predict the strength and microstructure, based on welding parameters, is required for designers to create safer solutions in engineering design. In this study, a 6 mm thick S960 low alloy ultrahigh-strength steel was welded using gas metal arc welding (MAG) and laser welding. The effects of welding heat input and operating temperature on the tensile properties, hardness, microstructure, and fracture mechanism of the welded specimens were investigated. The effects of operating temperature on the mechanical properties of welded joints were investigated by performing tensile tests between temperatures of −80 °C and + 400 °C. The unwelded base material was also tested in the same temperature range. The results showed a ductile fracture mechanism in all the samples regardless of the test temperature and welding heat input. However, the tensile strengths and elongations increased when the test temperature drops to −80 °C from room temperature. In addition, mathematical predictions for the strength and elongation properties, and grain sizes in heat-affected zones, as a function of temperature and welding heat input were proposed.
This paper studies the welding of X90 pipeline steel with ER100S-G welding wire via laser-metal active gas arc (laser-MAG) hybrid welding and explores the effects of three wire feeding speeds (8.5 ...mm/s, 9 mm/s, and 9.5 mm/s) on the microstructure, mechanical properties and corrosion resistance of the weld joints. The results demonstrate that the microstructure of the weld is composed mainly of acicular ferrite (AF) and massive ferrite (MF). The structure of the heat-affected zone (HAZ) is composed mainly of granular bainite (GB) and acicular ferrite (AF). As the wire feeding speed is increased, the weld and HAZ grains grow significantly, while the ultimate tensile strength and microhardness decrease. Polarization curves were obtained and electrochemical impedance spectroscopy (EIS) was conducted on welds and base metals. The base material has the highest corrosion resistance, and the corrosion resistance of the welds decreased as the grains grew.
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